When the Xenophon was attacked by Tyranids, it was Demetrios who called the Scythes to battle, under instruction from Hornindal, and witnessed the sergeants' final battle-oaths. He was last known to be leading the members of Sergeant Certes's squad in a desperate counter-assault, before the ship was lost to the xenos boarders.[1]

Demetrios was known to be aggressive and hateful, and had a reputation for being less than kind to the Chapter's serfs. Milus Ogden noted that he carried an "ever-present threat of violence'.[1]